Positioning measurements are an important feature of modern wireless communication networks. In the exemplary case of an emergency call from a mobile phone, the position of the mobile phone may need to be determined via a positioning measurement when the calling person is not capable of providing the corresponding information.
Positioning measurements in wireless communication networks are often based on timing measurements. In this regard, TDOA-based positioning approaches can be mentioned. TDOA is an abbreviation for Time Difference of Arrival and exploits timing information obtained from multiple RF receivers to calculate the position, or location, of a wireless device in communication with those receivers.
Positioning approaches based TDOA and similar techniques have advantages over positioning approaches that rely on Global Navigation Satellite Systems (GNSSs), such as the Global Positioning System (GPS) or GALILEO. First, the latter approaches require that the wireless device is actually equipped with a GNSS receiver, which might not be the case for certain classes of wireless devices (e.g., legacy phones). Moreover, the GNSS receiver, when present, also has to be in an active state. Since GNSS receivers have a considerable power consumption users often prefer to de-activate them unless specifically needed (e.g., for route guidance purposes). Still further, GNSS receivers require a clear “view” of multiple satellites for deriving a correct position. This condition is typically not fulfilled when a wireless device is operated indoors or in urban environments (i.e., when being surrounded by tall buildings).
As such, positioning approaches that rely on the infrastructure of a wireless communication network are often the only possibility to detect the location of a wireless device. On the other hand, TDOA and similar positioning approaches within a wireless communication network only function properly when a proper performance of the associated receivers can be guaranteed. For example, inaccuracies in timing measurements by the receivers will directly influence the accuracy of TDOA-based positioning.